Communication devices such as user equipments are also known as e.g. wireless terminals, mobile terminals and/or mobile stations. User equipments are enabled to communicate wirelessly in a cellular communications network or wireless communication system/network, sometimes also referred to as a cellular radio system or cellular network. The communication may be performed e.g. between two wireless terminals, between a wireless terminal and a regular telephone and/or between a wireless terminal and a server via a Radio Access Network (RAN) and possibly one or more core networks, comprised within the wireless communication network.
User equipments may further be referred to as mobile telephones, cellular telephones, laptops, tablet computers or phablets with wireless capability, sensors and actuators with wireless communication capabilities, just to mention some further examples. The user equipments in the present context may be, for example, stationary, portable, pocket-storable, hand-held, computer-comprised, or vehicle-mounted mobile devices, enabled to communicate voice and/or data, via the RAN, with another entity, such as another wireless terminal or a server.
The wireless communication network covers a geographical area which is divided into cell areas, wherein each cell area being served by an Access Node (AN) or a base station. The wireless communication network may include a number of cells that can support communications for a number of user equipments. A user equipment may communicate with a serving access node in a serving cell and may need to make measurements of other cells for various purposes. For example, for a user equipment to be able to monitor and eventually perform a handover to a neighbour cell, hereafter referred to as a target cell, the user equipment needs to receive signals from a target access node in the target cell, e.g. for mobility measurements, reading of system information or paging from the target cell, etc.
Wireless communication networks operating in millimeter wave frequencies typically apply transmit beamforming to enable link budgets for multi-Gbits/s transmissions. Beamforming is a signal processing technique used for directional signal transmission or reception. This is achieved by combining elements in a phased array in such a way that signals at particular angles experience constructive interference while others experience destructive interference. Beamforming can be used at both the transmitting and receiving ends in order to achieve spatial selectivity. The improvement compared with omnidirectional reception/transmission is known as the beamforming gain. Beamforming may be applied to physical channels used to transmit data to user equipments once their positions are known to the system. For broadcast transmissions, such as system information, paging, common reference signals, and synchronization etc. signals which are targeting user equipments not yet known to the network or user equipments which position is unknown to the network, it is a bit more tricky. Simple beamforming cannot be applied since it is not known in which direction to beamform. One common way around this problem is to transmit even those signals using beamforming but transmit them several times, each time into a different direction. This procedure is also called beam sweeping. An example of a system applying beam sweeping is IEEE802.11ad, the Wi-Fi standard operating in the unlicensed 60 GHz band.
If a user equipment is supposed to receive signals from a neighbour AN, which signals are transmitted using beam sweeping, it has to listen at all-time instances when the neighbour AN transmits. This is because the user equipment doesn't know when the neighbour AN transmits signals into the correct direction towards the user equipment. If the user equipment has only the capability to receive from a single direction it cannot receive data or signals from its own serving AN during this time which will reduce throughput.
WO2012115553 discloses that a communication device obtains information about an antenna beam of a beam sweeping base station in a cellular communication network. The information relates to when in time a time period starts and the duration of the time period. The communication device will only use the antenna beam during such a time period. When being out of the time period, the communication device refrains from attempting to receive or transmit data using the antenna beam. The document thereby addresses how to minimize the time of effort spent by the communication device to listen to a beam in the serving cell for reducing power consumption in the communication device. However, the document does not address listening to a neighbor (target) cell nor the throughput of the cellular communication network.